Association of hypophosphatemia, renal phosphate wasting (low TRP/low TmP/GFR), elevated FGF23 levels and paradoxically low or normal 1,25-dihydroxy vitamin D suggests the diagnosis of TIO after exclusion of the hereditary hypophosphatemic osteomalacia by adult onset of hypophosphatemia in the absence of family history and characteristic phenotype. Here, FGF23 is linked to hypophosphatemia.